Rotary screen printing with internally driven roller squeegee

ABSTRACT

A screen printing machine has two end pieces with a rotary screen attached thereto. A color tube extends axially inside the screen. A shaft positioned around the color tube drives a roller squeegee within the screen.

United States Patent [191 Bohm [ 1 ROTARY SCREEN PRINTING WITH INTERNALLY DRIVEN ROLLER SQUEEGEE [75] Inventor: Walter Bohm, Kirchbichl, Austria [73] Assignee: Peter Zimmer, Kufstein, Austria [22] Filed: June 21, 1972 [21] App]. No.: 264,988

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 3,312,165 4/1967 Strom 101/119 [4 May 21, 1974 Smith, Jr 101/119 3,408,984 11/1968 Pullins 101/119 X 3,592,132 7/1971 Weber 101/119 3,232,224 2/1966 Kramer 101/120 3,487,775 1/1970 Chaney 101/114 2,698,574 1/1955 Dougherty et a1.... 101/120 2,753,794 7/1956 Groak 101/120 X 3,352,234 11/1967 Londahl et a1 101/114 3,245,341 4/1966 Childress et a1. 101/122 Primary ExaminerRobert E. Pulfrey Assistant Examiner-R. E. Suter Attorney, Agent, or Firm-Wenderoth, Lind & Ponack 57] ABSTRACT A screen printing machine has two end pieces with a rotary screen attached thereto. A color tube extends axially inside the screen. A shaft positioned around the color tube drives a roller squeegee within the screen.

3 Claims, 2Drawing Figures PATENTEDHAYHI M 3311.378 SHEEIlOFZ Fig. 1

BACKGROUND OF THE INVENTION This invention relates to a screen printing machine with a rotary screen positioned between two end pieces, a color tube axially extending inside the screen and a driven roller squeegee.

The aforementioned machines have the advantage, compared with machines in which the roller squeegee is driven only by means of friction with the inside wall of the screen, that with synchronized drive of the screen and squeegee wear of the squeegee is practically eliminated. Furthermore, as is desired in certain cases, it is possible to provide for a predetermined difference in rotational speed between the screen and the squeegee.

However, the design of such machines having driven squeegees has heretofor been difficult due to space limitations. Particularly, when exchanging the screen the These difficulties increase when the end pieces of the screen have inwardly extending collar-like flanges, which facilitate easy mounting of the screen assembly and also prevent leaking of dye from the screen. Specifically, if the shaft on which the squeegee is mounted extends outwardly through the openings of the end piece flanges, and since the opening diameter is relatively small, the diameter of the squeegee must be relatively large. When this is the case, contact of the squeegee with the screen and thus penetration of the dye through the screenstarts very early, and the sharpness of the outlines of the print thereby suffer. Furthermore, the mounting of the squeegee within the screen is difficult. Attempts to overcome these problems by driving the squeegee with a shaft having universal joints results in inaccurate relative control of the screen and squeegee speeds, thus causing printing errors.

SUMMARY OF THE INVENTION The present invention solves the above prior art problems by arranging the shaft which drives the squeegee by means of gear wheels, friction wheels, chains or the like within the screen and mounted on the color tube. Thus, separate drive and support elements extending through the opening of the end piece for the squeegee are unnecessary, and the color tube and squeegee drive form a single unit. It therewith is possible to have the size of this unit and the diameter of the squeegee small enough to be inserted as a unit through the opening of the end piece. This is particularly true when the shaft is in the form ofa hollow shaft surrounding the color tube, as shown below with regard to a preferred embodiment of the invention.

Although in most cases it is desired that the speeds of the squeegee and screen be equal, occasionally different speeds may be desired. Either case may simply be attained with the squeegee drive according to the invention by adequate choice of the diameter of the gear wheels and the drive being effected from the drive wheel gear of the screen.

' mounting of the driving mechanism is time-consuming.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention is hereinafter described in detail with reference to the accompanying drawings, without being limited thereto, in which:

FIG. 1 is a longitudinal section of one end of a screen illustrating the invention; and

FIG. 2 is a diagrammatic view of a printing machine provided with a squeegee drive accordingto the invention.

DETAILED DESCRIPTION OF THE INVENTION The cylinder screen 1 of FIG. 1 is mounted on an end piece 2 in a manner not shown in detail. End piece 2 has a reduced diameter flange 3 having an inside diameter d. A gear wheel 4 is mounted on the flange of the end piece. The diameter D of the pitch circle of gear 4 is equal to the outside diameter of screen 1. Gear wheel 4 engages with a drive gear wheel 6 mounted on the support 5 of the machine. A color tube 7, whose ends are mounted in the support of the machine, axially extends through the opening of flange 3 into screen 1. Through color tube 7 dye is supplied in a manner known per se to the inside of screen 1.

A hollow shaft 10 is positioned coaxially around the color tube 7 and supported thereon by means of two fric'tion bearings 8 and 9. Two gear wheels 11 and 12 are fixed to hollow shaft 10. The gear wheel 11 is driven by the drive wheel gear 6 through anintermediate gear wheel 13, positioned on the machine support 5. The gear wheel 12 mates with another gear wheel 14 which is arranged on the end of a shaft 15 supporting a roller squeegee 17. The roller squeegee 17 is positioned in a collar 16 supported by the color tube 7.

The diameters of the gear wheels preferably are such that the circumferential speed of the squeegee is equal to the circumferential speed of the screen, whereby wear of the screen is substantially reduced. If however, as is known, the squeegee is provided with a laminated covering, for instance having ridges,'a slight speed differential is useful, in order to facilitate the bending or tilting of the ridges. The desired synchronization is achieved by providing that the ratio'of the diameters of the pitch circles of the gear wheels 11 and 12 is equal to the ratio of the diameters between squeegee 17 and the pitch circle of gear wheel 14. The dimensions are such that the distance a between the lowest point of the roller squeegee l7 and the uppermost point of gear wheel 12 is smaller than the inside diameter d of the opening in flange 3 of the end piece 2. This makes it possible to mount the squeegee along with its drive outside the cylindrical screen on the color tube and to thereafter insert the total unit.

In FIG. 2, the endless printer's blanket 18 runs over the front guide roller 22 and the rear, driven guide roller 23 in the direction of arrow 19. A drive shaft 21, which supplies rotary movement by means of helical gears 24 to the drive gear wheels 6 of a group of printing stations, is driven by means of a bevel gear drive 20 by the front guide roller 22.

At each printing station, the screen gear wheel 4, as well as the intermediate gear wheel 13, mesh with the drive gear wheel 6. The intermediate gear wheel 13 transmits rotary movement, by means of the gear sheel 11, to the shaft 10 and subsequently to the squeegee.

Numerous embodiments are possible within the scope of the invention. The drive of the squeegee could also be effected from the hollow shaft by means of chains, belts, friction wheels or the like a mathematical synchronization not being assured in the two last mentioned examples. It would also be possible to construct the shaft as solid shaft and to position it alongside the color tube.

What I claim is:

1. In a rotary screen printing machine including a rotary screen mounted on end pieces having openings therein, a color tube supply means extending into the interior of said screen through at least one of said end piece openings, a roller squeegee mounted within said screen to contact the inner surface thereof, and means for rotating said roller squeegee;

the improvement comprising:

said roller squeegee being supported by said color tube supply means; and

said means for rotating said roller squeegee comprising a tubular shaft rotatably mounted coaxially around said color tube supply means, drive means positioned without said screen for imparting rotary motion to said tubular shaft, and motion transmitting means positioned within the interior of said screen and operatively connected between said tubular shaft and said roller squeegee for rotating said roller squeegee.

2. The improvement claimed in claim 1, wherein said motion transmitting means comprises a first gear wheel mounted on said tubular shaft and a second gear wheel mounted on said roller squeegee, said first and second gear wheels being in meshing relation.

3. The improvement claimed in claim 1, further comprising gear means positioned without said screen for rotating said screen, said drive means being operatively connected to said gear means. 

1. In a rotary screen printing machine including a rotary screen mounted on end pieces having openings therein, a color tube supply means extending into the interior of said screen through at least one of said end piece openings, a roller squeegee mounted within sAid screen to contact the inner surface thereof, and means for rotating said roller squeegee; the improvement comprising: said roller squeegee being supported by said color tube supply means; and said means for rotating said roller squeegee comprising a tubular shaft rotatably mounted coaxially around said color tube supply means, drive means positioned without said screen for imparting rotary motion to said tubular shaft, and motion transmitting means positioned within the interior of said screen and operatively connected between said tubular shaft and said roller squeegee for rotating said roller squeegee.
 2. The improvement claimed in claim 1, wherein said motion transmitting means comprises a first gear wheel mounted on said tubular shaft and a second gear wheel mounted on said roller squeegee, said first and second gear wheels being in meshing relation.
 3. The improvement claimed in claim 1, further comprising gear means positioned without said screen for rotating said screen, said drive means being operatively connected to said gear means. 